<form action="<?php bloginfo('siteurl'); ?>" id="searchform" method="get">
  <div>
      <input type="image" alt="Submit" src="<?php bloginfo('template_url'); ?>/images/img-search.png" id="searchsubmit" />
      <input type="text" id="s" name="s" value="" class="rounded-equal" />
  </div>
</form>